Rule of Twelfths: from low to high tide in 6 hours and 13 minutes

How many times do you get perfect wind and wave conditions, but the tide is too low or too high? Learn the Rule of Twelfths and select the right time to go surfing.

Tides are a key factor when it comes to surfing and wave riding. Tide height affect the volume of water, that is the depth of water and the breaking of waves.

If the tide's too low, the chances of having too many close-outs are high, while if the tide's too low, wave might get mushy or slow-rolling waves.

The Rule of Twelfths is a rule of thumb for estimating the height of the tide at any time. Science tells us that the rate of flow of a tide increases smoothly to a maximum halfway between high and low tide, before smoothly decreasing to zero again.

This means that in the first hours, you'll notice that the tide might not rise/fall so much and it will accelerate the entire process in the mid hours.

Tide times available in tide charts usually tell you the exact hour and minute of low and high tides. The Rule of Twelfths applies to the semidiurnal tide - a tide having two high waters and two low waters during a tidal day, which is exactly what happens in most locations.

The semidiurnal tide period lasts of 12 hours and 25.2 minutes, that is from low to high tide and then to low tide, again. Learning what are the right moments to hit the surf - having in mind the Full/New Moon and First/Third Quarter Moon - will save you time and increase the quality of your session.

Discover how do the moon and sun affect tides and surfing? Check the tide times, charts and tables for your favorite surf spots. Learn how waves are formed.